“So,” said he, “he suspects me of suspecting him. Well, he is giving us every chance. But I think, Mayfield, you would do well to put Mrs. Monkhouse on her guard. If Wallingford makes a public parade of his feelings towards her, he may put dangerous ideas into the head of Mr. Superintendent Miller. You must realize that Miller is looking for a motive for the assumed murder. And if it comes to his knowledge that Harold Monkhouse’s secretary was in love with Harold Monkhouse’s wife, he will think that he has found a motive that is good enough.”
“Yes, that had occurred to me; and in fact, I did give her a hint to that effect, but it was hardly necessary. She had seen it for herself.”
As we now seemed to have exhausted this topic, I ventured to make a few enquiries about the rather farcical infernal machine.
“Did your further examination of it,” I asked, “yield any new information?”
“Very little,” Thorndyke replied, “but that little was rather curious. There were no finger-prints at all. I examined both the pistol and the jar most thoroughly, but there was not a trace of a finger-mark, to say nothing of a print. It is impossible to avoid the conclusion that the person who sent the machine wore gloves while he was putting it together.”
“But isn’t that a rather natural precaution in these days?” I asked.
“A perfectly natural precaution, in itself,” he replied, “but not quite consistent with some other features. For instance, the wadding with which the pistol-barrel was plugged consisted of a little ball of knitting-wool of a rather characteristic green. I will show it to you, and you will see that it would be quite easy to match and therefore possible to trace. But you see that there are thus shown two contrary states of mind. The gloves suggest that the sender entertained the possibility that the machine might fail to explode, whereas the wool seems to indicate that no such possibility was considered.”
He rose from the table—lunch being now finished—and brought from a locked cabinet a little ball of wool of a rather peculiar greenish blue. I took it to the window and examined it carefully, impressed by the curious inconsistency which he had pointed out.
“Yes,” I agreed, “there could be no difficulty in matching this. But as to tracing it, that is a different matter. There must have been thousands of skeins of this sold to, at least, hundreds of different persons.”
“Very true,” said he. “But I was thinking of it rather as a corroborating item in a train of circumstantial evidence.”